First freeze causes little damage to U.S. Northern Plains crops

CHICAGO (Reuters) - The U.S. northern Plains and far western Midwest crop regions saw their first freeze of the season but the cold temperatures were only in pockets of the belt, limiting damage to immature corn and soybeans, agricultural meteorologists said on Friday.

The forecast called for more cold temperatures in the northern Corn Belt on Saturday morning after lows on Friday morning ranged from the mid-20s to low-30s degrees Fahrenheit (minus 3.9 to 1.7 Celsius) from western Nebraska northward into the western Dakotas, Colorado and Montana.

"For the most part it wasn't a big deal in the major corn and soybean producing areas, the biggest crop areas were above the frost and freeze thresholds," said Andy Karst, an agricultural meteorologist at World Weather Inc in Kansas City.

The coldest spot was in northeastern North Dakota at Langdon which had a hard freeze, Karst said. The morning low dipped to 24 F ( minus 4 Celsius).

Crop specialists remain concerned about an early freeze hitting the northern states as corn and soybean are at least two weeks behind in development because of late planting and a cool summer. A freeze could take the top edge off this year's projected record-large harvest and lower crop quality.

Agronomists define a hard freeze as temperatures falling below 28 degrees F (minus 2.2 Celsius) for at least a couple of hours. At that point the plants shut down, halting kernel and pod filling. Even a mild frost would cut final yields, agronomists said this week.

The first killing frost in Iowa, the top corn state, usually comes in mid-October while the Dakotas, Minnesota and Wisconsin see one a week or two earlier.

U.S. Midwest map of frost dates: http://link.reuters.com/fuz82v

"Tomorrow there is a little more concern," said Josh Senechal, a meteorologist at Freese-Notis based in Iowa.

Senechal said the areas most susceptible to drop near freezing Saturday are in big corn and soybean country, including central and northern Iowa, southern Minnesota, western Wisconsin and eastern parts of the Dakotas.

"Other than tomorrow morning it looks like the frost threat is pretty limited late into the month," Senechal said.